These cheats are for the Daydream and Insomnia difficulties. First You'll have to bring up the console by pressing [~] and then type them in:
pkhaste - Toggle Haste.
pkweaponmodifier - Toggle 'Weapon modifier mode'.
weaponspecular - Toggles 'Weapon specular'.
pkhealth - Full Health.
pkammo - Full Ammo.
pkgod - God Mode.
pkweapons - All weapons.
pkgold - Add gold.
pkweakenemies - Toggle 'Enemies get 1 health point'.
pkkeepbodies - Toggle 'Bodies will never disappear'.
pkpower - Full ammo and health.
pkdemon - Toggle 'Demon morph'.
pkalwaysgib - Toggle 'Excessive gibbage'.
pkkeepdecals - Toggle 'Decals will never disappear'.